High speed lines are now being installed in the electronic industry to produce elongated, often magnetic devices in large quantities and at reduced costs. Such devices may comprise resistors, capacitors, varistors and diodes, quite often in the form of axially leaded devices. It is desirable that the leads of such devices be substantially straight when they are tested and later inserted into P-C boards. On the other hand, the assembly operations often cause the leads of such articles to be bent or deformed to such an extent that such leads should be straightened to make the articles usable.
Lead straightening generally relates to a recognized principle that when a nonlinear wire section is pressed between two opposing surfaces and one or both surfaces are translated, the section is rolled and tends to become straightened. When applying the rolling principle to articles having a body with opposing leads, it is advantageous to engage the leads close to the body and to progressively and simultaneously roll each lead away from such body. Many machines implement this combined principle, the major differences in the machines being in the means for transferring and transporting the articles through a straightening means.
It will be appreciated that substantial forces are applied to the leads by the engaging surfaces as such leads are rolled under pressure therebetween. These forces are desirably resisted by rugged means of article retention in order to maintain the elongated dimension of the articles transverse to the direction in which the articles are advanced.
Several different machines are employed to straighten leads in accordance with the above considerations. Some do an excellent job at relatively high efficiency but with low rates of production. By high efficiency it is meant that the machine cleanly picks up only one article at nearly every transfer movement, retains nearly every article as the articles are transport through the straightening means and delivers nearly every article in good condition after the leads have been straightened. Typically, this type of machine is complicated, costly to build and costly to maintain.
On the other hand, there are high speed machines available which are normally of moderate to low efficiency. A typical machine of this type is sold by B. Graule and Company K.G., of 1 Berlin 10, Helmholtzstr. 2-9, Germany, hereinafter called the "Graule" unit or straightener. The Graule unit is uncomplicated, relatively inexpensive and can be made to run over a wide range of speeds. However, conventional methods of orienting and feeding the articles into the deep slots required to retain the articles in the Graule unit usually limit the speed and efficiency of the operation.
In the past, the elongated articles were channelled by various means into raceways to maintain article orientation. From the raceways the articles were fed either directly onto a rotary transport member of a Graule unit or they were fed onto a transfer wheel which then fed the articles onto the transport member. These mechanisms were costly to build, costly to maintain and slow in operation. Later, magnetic bins were introduced to advantageously orient the articles.
Such bins are inexpensive to build and easy to fill because the magnetic field of the bin keeps the articles oriented when they are dumped from a handling box. Moreover, orientation is maintained even when the bin is not full so it has become common practice to feed transfer wheels directly from magnetic bins. This development has improved the cost and efficiency of Graule lead straightening but has done little to improve the speed of article transfer.